Electrical components often contain molded parts that are formed from a liquid crystalline, thermoplastic resin. Recent demands on the electronic industry have dictated a decreased size of such components to achieve the desired performance and space savings. One such component is an electrical connector, which can be external (e.g., used for power or communication) or internal (e.g., used in computer disk drives or servers, link printed wiring boards, wires, cables and other EEE components). Unfortunately, several different challenges exist for successfully forming liquid crystalline polymer parts for electrical components with a small dimension.
One problem with many conventional liquid crystalline polymers, for instance, is that they tend to display a very high solid-to-liquid transition temperature (“melting temperature”), which precludes their ability to flow well at temperatures below the decomposition temperature. To suppress the melting point and generate materials that can flow, additional monomers are often incorporated into the polymer backbone as a repeating unit. One commonly employed melting point suppressant is naphthalene-2,6-dicarboxylic acid (“NDA”), which is generally believed to disrupt the linear nature of the polymer backbone and thereby reduce the melting temperature. The melting point of the polymer may be lowered by substituting NDA for a portion of the terephthalic acid in a polyester of terephthalic acid, hydroquinone and p-hydroxybenzoic acid. In addition to NDA, other naphthenic acids have also been employed as a melt point suppressant. For instance, 6-hydroxy-2-naphthoic acid (“HNA”) has been employed as a melting point suppressant for a polyester formed from an aromatic diol and an aromatic dicarboxylic acid. Despite the benefits achieved, the aforementioned polymers still have various drawbacks. For example, the reactivity of the naphthenic acids with other monomeric constituents can have unintended consequences on the final mechanical and thermal properties of the polymer composition. This is particularly problematic for molded parts having a small dimensional tolerance. In addition to functional concerns, the high cost of naphthenic acids also dictates that the need for others solutions to the problems noted.
Of course, apart from the nature of the polymer itself, other challenges also exist in forming electrical components from liquid crystalline polymers. For instance, due to the manner in which they are employed, most electrical components are required to meet certain flammability standards. Typically, these requirements are achieved by adding flame retardants to the material formulations. However, some types of conventional flame retardants (e.g., halogenated retardants) are undesirable in electrical applications. Furthermore, such flame retardants can also have an adverse impact on the mechanical properties of the resulting molded part.
As such, a need exists for a low naphthenic, liquid crystalline thermoplastic composition that can be more readily formed into a small dimension part, and yet still attain good mechanical and/or flammability properties.